Barley SS2a single base mutation at the splicing site led to obvious change in starch

Starch biosynthesis is a complex process that relies on the coordinated action of multiple enzymes. Resistant starch is not digested in the small intestine, thus preventing the rapid rise of the glycemic index. Starch synthase 2a (SS2a), a key enzyme in amylopectin biosynthesis, has significant effects on starch structure and properties. In this study, we identified an ss2a null mutant (M3-1413) with a single base mutation from an ethyl methane sulfonate (EMS)-mutagenized population of barley. The mutation was located at the 3´ end of the first intron of the RNA splicing receptor (AG) site, resulting in abnormal RNA splicing and two abnormal transcripts of ss2a, which caused the inactivation of the SS2a gene. The starch structure and properties were significantly altered in the mutant, with M3-1413 containing decreased total starch and increased amylose and resistant starch levels. This study sheds light the effect of barley ss2a null mutations on starch properties and helps to guide new applications of barley starch to develop nutritious food products.